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The prominent benefit of granite is owned to its physicochemical property and ubiquitous nature. Vast application of granite which also includes its use as an adsorbent in environmental remediation practice, can also be enhanced. To further enhanced the uptake capacity of granite, nanocomposite consisting of multiwall carbon nanotubes (MWCNTs) and granite was fabricated and further modified using Dialiumguineensestem bark extract. The structure and composition of pristine granite (PG) and modified nanocomposite granite (G) based material were examined and confirmed by the FTIR, Raman, TGA, SEM and XRD. Meanwhile, the specific surface areasof PG (1.268 m2/g) and G (16.57 m2/g) were obtained using the BET surface area analyser. The optimization step revealed that the uptake capacities of PG and G were dependent on solution pH, sorbent dose and contact time. Meanwhile, pseudo-second-order and Elovich kinetic models were noticed to best describe the data for the removal of Cr (VI) by PG and G. Equilibrium isotherm study revealed that Freundlich and Langmuir models fitted well to the experimental data obtained for the uptake of Cr(VI) onto PG and G respectively. Furthermore, electrostaticattraction betweentheDialiumguineense stem bark extract on the surface of G and Cr(VI) influenced the uptake of Cr(VI). On the other hand, the interaction between the plant extract and Cr(VI) may result in the attenuation of Cr(VI) via reduction to Cr(III). Finally, the thermodynamically favoured adsorptive process demonstrated high adsorbent reusability with good stability for Cr(VI) uptake. [ABSTRACT FROM AUTHOR]

This study assessed the adsorptive uptake of Cr(VI) onto eco-friendly adsorbent fabricated via the surface coating of pristine dolerite (PD) using the extract ofAzadirachta indica stem bark. The materials were characterised using the XRD, FESEM, FTIR, EDX, BET and Raman analysis. Optimum adsorption of Cr(VI) onto AMD was achieved at pH = 2, contact time of 180 min and dosage of 0.03 g. The adsorption equilibrium data for PD and Azadirachta indica extract modified dolerite (AMD)fitted well with the Langmuir and Redlich-Peterson models respectively at 318 K.Also, a good correlation between the experimental data and the Elovich kinetic model was achieved. The diffusion mechanisms were both controlled by film diffusion and intraparticle diffusion.The uptake of Cr(VI) onto PD and AMD was feasible, endothermic (ΔH: PD = 14.14 kJ mol−1 and AMD = 37.67 kJ mol−1) and entropy-driven (ΔS: PD = 17.69 J K−1 mol−1 204.3 J K−1 mol−1). Besides, the recyclabilitypropensity of AMD afterseveral cycles projects AMD as a fibrousbasedmaterialwithsustainablepotential for the decontamination of Cr(VI) polluted water. [ABSTRACT FROM AUTHOR]

This study investigates the capacity of spent self-indicating silica gels modified with Harpephyllumcaffrum(wild plum) stem bark extract to remove hexavalent chromium from wastewater. The physicochemical properties of the adsorbents were assessed using FESEM, FTIR, PXRD, TGA and BET surface analyser. The batch adsorption technique was used to examine the capacity of spent self-indicating silica gel (SIPP) and modified spent self-indicating silica gel (SIP) to eliminate Cr(VI) from the aqueous solution. The uptake capacity of the sorbents was noticed to increase with increasing adsorbent dose, contact time and initial concentration of Cr(VI). On the contrary, the potential of SIPP and SIP were observed to decline with increasing solution pH, similarly as found for most Cr(VI) absorbents. However, the uptake capacity of the SIPP and SIP were noticed to be optimum at 0.05 g adsorbent dosage and 180 min contact time. Meanwhile, the kinetic behaviour of SIPP and SIP in the removal of Cr(VI) was best described by the Elovich kinetic model. Furthermore, the uptake of Cr(VI) onto SIP and SIPP was sufficiently described by the three-parameter isotherm Sips and Freundlich isotherms respectively. The Cr(VI) adsorption was endothermic, entropy-driven, and feasible. The application of Harpephyllum caffrumstem bark extract on SIPP as Cr(VI) adsorbent was significant and the reusability of the adsorbent portrayed the capacity of SIP to adapt to a full-scale wastewater treatment practice. [ABSTRACT FROM AUTHOR]

This study presents the fabrication of nanocomposite for the sequestering of Cr(VI) from solution. The nanocomposites were obtained from the molecular sieve and functionalized multiwall carbon nanotubes and further modified with Pentaclethra macrophylla (oil bean tree) stem bark extract. The pristine molecular sieve (MS) and the modified nanocomposite [Pentaclethra macrophylla stem bark extract anchored on molecular sieve (SMP)] adsorbent were characterized by the FTIR, FESEM, XRD, BET, and TGA techniques. The batch adsorption experiment revealed an agitation time of 120 min, 0.02 g dosage, and sorbate pH of 2.0 as optimum conditions for effective use of MS and SMP. Under these conditions a maximum monolayer capacity (qmax) of 135.5 mg g−1 was obtained for SMP, a value that is better compared to many other related absorbent materials. The uptake of Cr(VI) onto MS and SMP was best described by pseudo-first-order and Elovich kinetic models respectively. Meanwhile, the Freundlich model was noticed to sufficiently describe the isotherm data obtained for MS and SMP. The adsorption of Cr(VI) onto MS and SMP was spontaneous, endothermic, and entropy-driven. The reusability of the nanocomposite and its efficient Cr(VI) removal, present SMP as a potent adsorbent for the sequestration Cr(VI) from aqueous solution. nsufficient innovative research on the sequestration of Cr(VI) from the aquatic ecosystem has made Cr(VI) a recalcitrant water contaminant that often affects water sources. In this work, a novel plant anchor-nanocomposite was fabricated from the spent molecular sieve, multi-walled carbon nanotubes, and the extract from the stem bark of Pentaclethra macrophylla. It was envisaged that due to the phytochemical constituent of the modifier, this nanocomposite could also act as potent adsorbents for the treatment of Cr(VI) polluted water. To the best of our knowledge, the application of Pentaclethra macrophylla stem bark extract as a modifier for the green fabrication of nanocomposite has not been reported. The resulting composites showed good uptake capacity for Cr(VI) as well as efficient reusability. [ABSTRACT FROM AUTHOR]